Book/Report

FZJ-2019-01523

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Zur Kinetik atomarer Prozesse auf der Pt(111)-Oberfläche

Hohage, M. (Corresponding author)FZJ*

1996
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/21695

Report No.: Juel-3255

Abstract: The kinetics of the Pt (111)-surface has been analyzed by scanning tunneling microscopy (STM). Three qualitatively different types of kinetic mechanisms have been found to be active under the analyzed conditions: (i) various atomic hopping processes on the surface which determine the low temperature island growth, (ii) the incorporation of adatoms into the surface which takes place in addition during growth at temperatures above 400K, and (iii) the slip of dislocations caused by adsorbates. The decisive atomic processes which determine the shapes of islands during the low temperature (T<300K) growth ofPt on Pt(111) have been traced by the comparison of STM-measurements with kinetic Monte Carlo (MC)-simulations. The dendritic island shapes and the temperature dependence of the branch thickness of the islands grown up to 265K are reproduced accurately by implementing a strong asymmetry in the movement of onefold coordinated atoms. To explain the island shapes between 265K and 300K besides the movement of onefold coordinated atoms also the movement of the twofold coordinated step adatoms has to be taken into acount. During growth at higher temperatures (T>400K) a reconstruction of the Pt(111)surface appears: due to the naturally existing tensile stress, some of the deposited adatoms are incorporated into the surface layer resulting in a reconstructed surface. The atomic structure and the mesoscopic appearance of the reconstruction have been analyzed in detail. Furthermore the evolution of the reconstruction from its nucleation to a dense reconstruction network has been studied. The metastable character of this deposition induced reconstruction is evidenced by annealing experiments where at temperatures high er than 650K the thermal decay of the reconstruction takes place. Finally the influence of adsorbates on the metastable reconstruction has been analyzed. It turns out that adsorbates (O, CO, and H) cause the lifting of the reconstruction even at low temperatures. The lifting of the reconstruction takes place by ejection of the previously incorporated Pt-atoms. These ejected atoms form atomic Pt-chains or small Pt-clusters on the surface, which have been analyzed in dependence of the adsorbate. In the case of Hand CO the lifting process goes hand in hand with a strong mass transport inside the surface layer by dislocation slip.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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